This is a good question, but you will not get a true sense of whether they both do contribute equally, or not.
Those that do, will boast about it and those that don't will deny it, and the spouses who feel they are doing more that their other half does will certainly voice their opinions the loudest, even if what they say is true or not. L.O.L.
Ideally, if both of the couples living together have equal status in the work place, they should both contribute equally. OR, if one partner works and the other stays home with children, then the one staying at home should be doing the majority of chores around the house (with the help of the children of course).